The invention relates to systems for suspending and cooling refractory furnace roofs.
High temperature furnaces have roof structures comprised of refractory bricks. The bricks are supported from hanger beams by metal hangers. A number of systems are known whereby the bricks interlock with one another so that the number of hangers may be reduced. Nevertheless, a large number of these hangers typically protrude from a furnace roof, making it difficult to keep the roof free of dust and debris, thereby hindering heat removal from the roof refractory and hence reducing its service life.
Generally, furnace roof suspension systems do not include means for cooling the refractory bricks comprising the roof. One exception is the system disclosed in U.S. Pat. No. 1,404,845 (Gates), issued on Jan. 31, 1922. This patent discloses a furnace xe2x80x9carchxe2x80x9d having a grid of interconnected tubular members through which coolant is circulated. Inlets for the coolant are provided in the longitudinal tubular members and outlets for the coolant are provided in the transverse tubular members. The refractory bricks comprising the arch are notched for support from the longitudinal tubular members, while the ends of the transverse tubular members rest on the furnace walls, thereby supporting the roof.
The Gates patent shows two different arrangements for constructing an arch. In one arrangement, shown in FIG. 1 of Gates, the tubular members 15 are inserted into channels between the bricks from above, therefore requiring the use of wedges or fillers to hold the bricks in suspension. In a second arrangement, shown in FIG. 4 of Gates, a cooling tube is required between each pair of bricks.
Although the Gates system provides some advantages over conventional hanger systems, the grid of transverse and longitudinal tubular members may interfere with the ability to remove dust and debris from the furnace roof. This cleaning is essential for maximum roof life, as the dust is insulating and, if not removed, will cause the bricks to run hotter, thus reducing their life. Furthermore, it appears that the refractory bricks of the Gates furnace arch cannot be replaced from above, but rather must be replaced from inside the furnace, requiring a furnace cold shutdown and consequent loss of production.
In addition, supporting the roof on the walls as disclosed by Gates is undesirable in that the roof must be removed or otherwise supported to replace the wall bricks, which must typically be done much more frequently than roof repairs.
In order to address these deficiencies in the prior art, it is desirable to provide an improved system for suspending and cooling a refractory furnace roof.
The present invention overcomes the disadvantages of the prior art by providing a system for supporting the roof of a furnace, the system comprising a plurality of elongate roof support members extending across the furnace, with the bricks of the furnace roof being supported by support surfaces on the sides of the roof support members in such a manner that the bricks are removable from above the roof. The roof support members are preferably provided with at least one interior coolant passage which circulates a cooling fluid between a coolant inlet and a coolant outlet. In the preferred embodiment, the roof support members thus simultaneously serve the dual purpose of both supporting and cooling the bricks.
In the system according to the invention, the need to attach hangers to individual bricks is eliminated, and the bricks can be removed and replaced from above without shutting down the furnace to a cold state, thereby greatly simplifying and shortening the time duration and expense of repair procedures. Furthermore, in the preferred system of the invention, the coolant inlets and outlets are provided in the roof support members, thereby eliminating the need for coolant-carrying cross members as in the Gates patent.
In one aspect, the present invention provides a roof for substantially covering an interior space of a furnace, the furnace roof comprising: a plurality of elongate roof support members extending across a top of the furnace, with spaces being provided between adjacent roof support members; a plurality of refractory bricks provided in the spaces between adjacent roof support members, the roof support members and refractory bricks substantially completely covering the interior space, wherein the bricks are arranged in rows extending along the roof support members, with at least one row of bricks being provided between adjacent roof support members, each of the bricks having a bottom surface facing the interior of the furnace, a top surface facing away from the interior of the furnace, and a pair of opposed side surfaces extending between the top and bottom surfaces; and each of the roof support members having opposed sides extending along substantially its entire length, at least one of the sides being provided with a support surface which is in direct contact with the side surfaces of a plurality of the refractory bricks of one said row of bricks, and upon which said plurality of refractory bricks is at least partially supported, wherein the side surfaces of the bricks and the sides of the roof support members are shaped such that the bricks which are in direct contact with the support surface of the roof support member can be removed from the space between adjacent roof support members by raising the bricks from above the roof.
In another aspect, the present invention provides a support member for supporting a plurality of refractory bricks in a furnace roof, the support member being elongate and having a first end, a second end and a pair of opposed sides extending along substantially its entire length, each of the sides being provided with a support surface for supporting said refractory bricks, wherein said support surfaces each comprise a shoulder forming a transition between upper and lower portions of one of one of the sides, such that a width of the roof support member between the upper portions of the sides is less than a width of the roof support member between the lower portions of the sides.